Russian Navy frigate Admiral Grigorovich fired several warning shots at a yacht in the English Channel, U.K. media reported on June 16.The incident involved a British-flagged civilian vessel around 11:40 p.m. local time off the Isle of Wight, Sky News reported, citing the Press Association.The U.K. Defense Ministry is investigating the reports of the incident.Citing British military sources, U.K. newspaper The Telegraph reported that the Admiral Grigorovich had been in and around the channel for a few days, escorting tankers of Russia's so-called "shadow fleet," foreign-flagged vessels used to transport Russian oil and other exports while evading sanctions. The incident comes just two days after Prime Minister Keir Starmer announced a raid on a shadow fleet vessel, in one of the rare Royal Marine commandos and specially trained officers from the National Crime Agency intercepted the vessel, Smyrtos, in the early hours, with Starmer's personal authorization.The operation lasted around six hours and was described as the first U.K.-led operation of its kind.“This successful operation delivers yet another blow to Russia and reminds those fueling Putin's war in Ukraine that we will not let them hide,” Starmer wrote on X.According to the Telegraph's sources, the warning shots fired by the Admiral Grigorovich were not connected to the seizure of the Smyrtos.No injuries or damage were reported. The Kyiv Independent is not able to independently verify details of the incident.The UK has sanctioned almost 600 Russian shadow fleet vessels to date.The shadow fleet of more than 700 vessels transports around 75% of Russia’s sanctioned oil and serves as a key source of revenue for the Kremlin, according to recently-appointed UK Defense Secretary Dan Jarvis. The income generated for the Russian state by the fleet's activities remains a key enabler of Moscow's war machine.Several countries, including France, Germany, and Italy have taken action against Russian-linked vessels in their territorial waters. Most recently, the French Navy detained a Russian shadow fleet tanker in the Atlantic Ocean on May 31.